Electromagnetic core



March 1s, 1941. E E FRANZ 2,235,425

ELECTROMAGNETIC CORE FIG. 3

A Tram/Ey Patented Mar. 18, 1941 UNITED ASTATES PATENT OFFICE ELEc'rRoMAGNETIc CORE Application December 9, 1938, Serial No. 244,729

6 Claims.

'I'his invention'relates to electromagnetic coils and more particularly to electromagnetic coils having laminated cores assembled from sheet metal elements.

Coils are used in an endless variety of forms and ways in electrical apparatus, and generally speaking fall into two great classes, coreless coils and cored coils in which the windings surround cores of magnetic material. Cored coils very frequently are made with cores built up from assembled laminae of sheet material, in order to diminish energy Waste due to eddy currents in the body of the core. Much ingenuity has been expended upon Ways of manufacturing such laminated cores in order that the making of the cores and the assembling of the cores and their Windings may be as simple, cheap and wasteless as possible. For various reasons diiiiculties have been encountered. Coils have been produced satisfactorily with cores which are wasteless in production, but with which the Winding must be prewound on a spool or other support and then installed bodily upon the assembled or partly assembled core. In such structures space is taken up and wasted so far as the eiciency of the coil is concerned by the spool or support on which the coil is Wound. Other laminated core coils have'been produced in which the winding of the conductor has been done directly on the assembled or partly assembled core without the need 'of any special Winding Spool or frame. However, in many instances the laminae for assembling such cores cannot be produced wastelessly. Further-V more, in cases Where the core is assembled in a prewound winding, the mechanical working of the laminar core material when the laminae are clamped or riveted together inay seriously damage the magnetic properties of a core made of some of the recent high' permeability alloys; and such cores cannot be then annealed to restore the desired properties with the insulated windings in place on them',

An object of the present invention is to provide u a. coil structure and-a laminated core for a coil which shall present a coil having a core and winding combinable substantially without any electrically useless winding spool, frame, or the like, in which the 'laminar Vcore is composed of 50 elements produced from sheet material in which a considerable range of ratio of winding volume to core is possible, which is adaptable equally to' such constructions as shell typev and core type transformers among others, and in which Vthe Il core is so constructed that no working of the core material is required after the windings are installed.

With the above and other objects in view, a

typical embodiment of the invention may comprise a coil having a core built up of layers, each 5 layer consisting of two or more equally tall flat pieces punched or otherwise formed from magnetic sheet material, of which pieces ,one outer one may be a short armed C, the middle piece an H lying on its side and having long arms 10 abutting the arms of the short armed C and short arms on its other side, and another outerpiece a long armed C whose arms abut the short arms of the middle piece. In other forms, the H- shaped piece may be omitted, or itself comprise l two C-shaped pieces.

Other objects and features of the invention will appear from the following detailed description of embodiments thereof taken in connection with the accompanying drawings in which the 20 same reference numerals are applied to identical parts in the several figures and in Which- Fig. 1 is a diagrammatic view of a strip of magnetic sheet material to show the wasteless production of core lamina parts therefrom; l5

Fig. 2 is a plan View of a core composed of the laminar parts of Fig. 1;

Fig. 3 is an enlarged sectional view on the line Fig. 4 is a plan `view of a coil wound on the core 30 shown in Fig. 2;

Fig. 5 is a view similar to Fig. 1 of a modied form;

Fig. 6 is a view thereofgcorresponding to Fig. 2; Fig. '7 is a view similar to Fig. 1 of another 35 modified form; Y

Fig. 8 is a view thereof corresponding to Fig. 2; Fig. 9 is a view similar to Fig. 1 of. a third modied form;

Fig. 10 is a view thereof corresponding to 40 Fig. 2;

Fig. l1 is a view thereof corresponding to Fig. 3;

Fig. 12 is a view corresponding to Fig. 1 of a fourth modified form;

Fig. 13 is a view thereof corresponding to Fig. 2. Fig. 1 may be thought of as a ribbon of magnetic sheet material from which laminar pieces are to be cut for subsequent assembly into units of an electrical coil core, and on which the pieces are laid out to show how they may be cut from a parallel sided ribbon substantially without scrap or waste. There are three kinds of pieces shown, viz. C-shaped pieces indicated at 20 having relatively long arms 2 I, c-shaped pieces indicated at 55 22 having relatively short arms 23, and H-shaped pieces indicated at 24 having relatively long arms 25 on one side and relatively short arms 21 on- "the other side.

The C-shaped pieces of both kindshave holes 2s, through which asserhbhng rivets 30 are to be passed later, in the centers of the backs of the Cs, midway of both the length and width of the backs of the Cs. The H-shaped pieces have similar holes 28 near each end located at the two intersections of the -axis of the crossbar of the H with the two axes of the arms. It will be noted that the adjacent long arms 25 oi any two neighboring Hs are enclosed within and exactly ll the recess of a C 2U, that adjacent long arms 2| of any two neighboring Cs 20 are enclosed within and exactly fill the recess be tween long arms 25 of an H, that the adjacent short arms 2l of any two neighboring Hs are enclosed Vwithin and exactly ll the recess of a C 22, and that adjacent short arms 23 of any two neighboring Cs 22 are enclosed within'and exactly fill the recess between short arms2'l of an H. Hence there is no scrap orvwaste when the pieces shown are punched or otherwise cut from the ribbon except the insignificant and unavoidable scrap or chips from the punching or drilling of the holes 26.

The three kinds of pieces shown in Fig. 1 having been prepared vin suiiicient number, are assembled by stacking and riveting into the three ,/units shown in Fig. '2 at' 3|, 32 and 33, respectively. 'I'he unit 3| .is a stackof the twokinds of C-shaped pieces, 2U and 22, piled in alternation, a 22 `at the top followed by a 20 and a 22 and a 20 and so on downward, with their arms in conto the unit 3|, except that the pile. begins at the top with a C 20. The unit 32 is a pile of H-shaped pieces only laid with the crossbars 23 in superimposed congruence and the long and short arms extending.

alternately tothe left and right. This stack or unit -32 has allof its surfaces substantially smooth except the four extremities of` its arms, which are recessed to correspond on one side tothe projections between the recesses of the arms of the unit 3| and on the other to those of the unit 33.

The three stacks having been piled as, described y independently of each other, may be riveted, re-

spectively, with rivets 30, or otherwise bound to form rigid units. l i

` The material of the core pieces 20, 22 and 24 in 'some instances will preferably be of silicon steel or ofl one or another'of -the high permeability nickel iron alloys known as permalloy. These materials may be given an extremely high Dermeability,` or rententivity, 'or low hysteresis, or other desirable electromagnetic'character hyv apprbpriate heat treatment. 'I'hese materials, however, are extremely sensitive to mechanical working, or even. shock, after having been so heat treated; and any slight working, such as that caused by the seatingA and swedging over of the. rivets 30 inthe present instance, may seriously impair the particular-characteristic ofthe material. t

In employing the present -invention therefor,

the heatv treatment is deferred until the three units, 3|, 32 and 33 are individually complete as described, i. e. stacked and riveted, since, accordlated conductor may be done by hand or, preferably, by any suitable winding machine, until the requisite number of turns is in place on the unit 32. The .units 3| and 33 are then assembled with the unit 32toembrace the winding as shown in Fig. 4 and to-have the relations to the unit 32 best shown in Figs. 2 and 3.

The complete core, shown in Figs. 2 and without the winding 34, consists essentially of successive layers, each vlayer consisting of one H-shaped piece and two unlike C-shaped pieces. rllhe top layer as shown has a C 22 at the left, the ends of whose short arms 23 abut directly against the ends of the long arms 25 of an H 24.

' The ends of the short arms 21 of the H 24 abut directly against the ends of the long arms 2| of a -C 2 0. The second layer has identically similar elements but in reverse order. Every odd num- `-bered layer is identically like the rst, and every even numbered layer like the second. From this it follows that the division between the units 3| and 3 2 or between the units 32 and 33 is not a substantially sn'iooth plane, y but is a square angled zigzag with elements of one unit overlapping elements of the other by an amount equal to the difference in length of 23 and 2|. This zigzag overlapping at the joints brings two desirable results. First, the gap reluctance of the assembled cores magnetic paths at the joints of the units is materially diminished as compared with a core where the corresponding joint is a. plane face and there is no lateral contact between parts of the units. Secondly, the interfltting of the projections and recesses of the units provides a modicum of mechanical support of the unitsby each other and of frictionalresis'tance to separation ofthe units, which renders the assembled core or coil much easier to handle and mount, duevregard being had to the sensitivitiy of the material to shock or deformation.

It is also of importance that the H-shaped unit 32 o iiers no obstruction to the Winding of I Fig. 4, the entire cross section of each ofthe apertures or windows ofthe core is available to be filled with windings, as none of` the window space need .bewasted either to receive an electro` magnetically inoperative winding spool or frame, or by clearance oversize internally and imdersize externally of a prewound coilformed with adhesive or other means lto maintain its form while being assembled on the core.

The core shown in Figs. 1 to 4- has the mum symmetry in all ways possible to this 'mode of construction. I'he windows 'are square, the

-bar of the H is of the same shape and size as the windows, and each side of a. window not made by the crossbar is the same size and shape as half maxithe crossbar or window. The core cross section of the magnetic path is the same throughout, assuming that the flux divides equally on leaving the crossbar to pass around the two windows.

Figs. 5 and 6 correspond in every way, respectively, to Figs. 1 and 2 except that the proportions of the Cs, 520 and'522, and of the Hs, 524, are such that the windows are lengthened transversely to the crossbar and the magnetic path is diminished in cross section. The ratio of magnetic material to conductor material is substantially diminished.

Figs. 7 and 8, corresponding, respectively, to Figs. 1 and 2, are presented to show in 'one embodiment both how the windows may be shortened transversely to the crossbar and the magnetic path increased in cross section 'and how the magnetic path may be unbalanced if desired for any reason by altering the proportions of the Cs, |20 and 122, and of the Hs, 124.

In both Figs. 5 and 7, however, the scraplessness of Fig. 1 is retained, as is the overlapping interfitting of the three units in each case also.

To eiect this intertting so that not only will the intertting occur, but also all facesof each unit except the interttable ends of the arms shall be substantially smooth, the following conditions are believed, from a study of Figs. 1, 5 and '7, to be necessary and suflicient. The widths KM and WN of the backs of the C-shaped pieces must be equal. The widths JQ and AG of the C arms must be equal as also the Widths GR and QP of the C arms. The widths KZ and WS of the H arms must be equal as also the widths SD and ZB of the H arms. And the lengths DJ and AB of the C arms must -be unequal as also the lengths DJ and AB of the H arms. Finally, the

widths SD and GR as also the widths WS and AG of the H arms and Clarins to be abutted in one layer ofthe core, must be respectively equal.

To effect the scrapless production of the parts in the manner shown in Figs. 1, 5 and 7, it is necessary and sufficient that: The sums of the widths.JQ and QP and of the Widths AG and GR of the upper and lower Cs, respectively, be equal to the distances JP and AR between the arms on the corresponding side of the H; the sums of the widths KZ and ZB and of the Widths WS and SD of the arms of the H-respectively must be equal to the distances KB and WD, respectively, between the arms of each corresponding C; and the lengths AB- and JD of the H arms must be respectively equal to the lengths AB and JD of the C arms.

In Figs. 9, 10 and 11 is shown a manner in which substantially the same result' is achieved by the use of C-shaped pieces only. Fig. 9 represents, in effect, the ribbon shown in Fig. 1 separated longitudinally into two vribbons along a line lying above the center of the ribbon of Fig. l, and with the central row of perforations 26 replaced by two rows, one in each ribbonof Fig. 9. The C-shaped pieces 20 and 22 of`Fig. 9 are identical with 20 and 22, respectively, of Fig. 1 in form. Each H-shaped piece 2l of Fig. 1,.how ever, is now split into or replaced by two C-shaped pieces |24'a-nd 224. Figs. 10 and 11 show how a laminar core is assembled from these pieces with four pieces, one of each kind, in each layer and forming four `units. Units 3| and 33 are identical with units 3| and 33 of Fig. V2 in form and structure, but unit 32 of Fig. 2 is split into or replaced by two units |32 and 232 in Fig. 10. Units |32 and 2-32 put together are substantially identical inform with unit 32.

. side.

In making a coil like that of Fig. 4 but with a core like that of Fig. 10, units |32 and 232 are first stacked and riveted independently of each other and heat treated and then assembled together into one H-shaped unit by interfitting the backs of the C-shaped pieces of which each is composed. Such an object has suiilclent stability and coherence by virtue of this interfitting to permit of being handled as a single unit whilethe winding is being put on as in the case of the coil of Fig. 4. Then, as before, the winding being finished, the units 3| and 33 are assembled with the wound central unit.

In Figs. 12 and 13 there is shown a coil structure based on the same general principles, although the shapes of the pieces are superficially different, and to attain the same general results. Here the central unit 332 consists of stacked H- shaped pieces with the ends of the arms formed with notches 35, and with long arms 36 alternating with short arms 31 around the H. In the unit 332, these H-shaped pieces are stacked with long and short arms alternating over each other.

In cutting the various pieces, of vwhich there are only two kinds, as shown in Fig. 12, a set of four perforations 26. is rst punched in the strip or ribbon at an operating station indicated at I. At station II an L-shaped piece 320 is punched out. At station III a second L-shaped piece 322 is punched out. and at station IV the H-shaped piece 324 is cut oil.

'Ihe two L-shaped. pieces are identically alike and interchangeable in assembly. Each is formed and proportioned to have the notched top of its long arm abut and fit accurately into notch 35 of either long arm 36 lof the H-shaped pieces while its short arm extends into and fits the notch 35 of the short arm of the H on the same These L-shaped pieces are stacked in the units 33| and 333 with their short arms alternately at each end of the unit but all on the same side of the unit, thus creating a substantially C-shaped unit to combine with the centrai H-shaped unit as in the previous constructions.

The unit 332 may then be Wound as in the preceding cases and the units 33| and 333 assembled therewith in the same manner, to intert in subfaces of the ends of the arms of all three units will then be substantially smooth and the units may then be abutted withoutl intertting. Such a structure with coils on all three units could then be used wherevervariable inductive coupling between coils is desired by separating or approximating the wound units.

'I'he embodiments of the invention herein disclosed are illustrative and in their variety show that they may be modified and departed from in many ways without departing from the spirit and scope of the invention as pointed out in and limited-solely by the appended claims.

Certain subject matter shown but not claimed in this application is claimed `in my divisional application S. N. 338,060.

What is claimed is:

1. A laminated electromagnetic core comprising a plurality of laminae of magnetic material piled ina stack, each lamina consisting of a C-shaped piece and an H-shaped piece and a C-shaped piece in that sequence, one -shaped piece having short arms and the other C-shaped piece having Ilong arms and the H-shaped piece having short arms on one side o! its crossbar and long arms on the other side, the ends of the short arms of the one C-shape piece being abutted against the ends of the long arms of the H-shaped piece and the ends of the long arms of the other C-shaped piece being abutted against the ends of the short arms of the H-shaped piece, and the pieces of each lamina overlapping the joints of each next lamina.

2. A laminated electromagnetic core comprising a plurality of laminae of magnetic material piled in a stack, each lamina consisting of a C-shaped piece and an H-shaped piece and a C-shaped` piece in that sequence, one C-shaped piece having short arms of the one C-shaped piece and of the Hfshaped piece being all equal, and the lengths of the long arms of the other c-shaped piece and of the H-shaped piece being all equal.

3. A laminated electromagnetic core comprising l a plurality of laminae of magnetic material piled in a stack, each lamina consisting of a C-shaped piece and an H-shaped piece anda C-shaped piece in that sequence, one c-shaped piece having short arms and the other C-shaped piece having long arms and the H-shaped piece having short arms on one side of its crossbar and long arms on the other side, the ends of the short arms of the one C-shaped piece being abutted against the ends of the long arms of the H-shaped piece and the ends of the long arms of the other C-shaped piece being abutted against the ends of the short arms ofy the H-shaped piece, the lengths of the short arms .of the one Q-shaped piece and of the H-shaped piece being all equal, the lengths of the long arms of the other C-shaped piece and of thc H-shaped lpiece being allequal, and the widths of 4abutted arms being equal.

4. A laminated electromagnetic core comprising a plurality of laminae of' magnetic material piled in a stack, each lamina consisting of a c-shaped pieceA and an H-shaped piece and a C-shaped. piece in that sequence, one 0shaped piece having short arms and the other c-shaped piece having long arms and the H-sha'ped piece. having short arms on one side of its crossbar and long arms on the other side, the ends of the short arms of the one C-shaped piece being abutted against the ends of the long arms of the H-shaped piece and the ends ofthe long arms of the other C-shaped piece being'abutted against the ends of the short arms of the H-shaped piece, the lengths of the short arms of the one C-shaped piece and the H- shaped piece being all-equal, the lengths of the long arms of the other C-shaped piece and of the H-shaped piece being all equal, and the pieces of each lamina overlapping the joints of each next lamina.

5. A laminated electromagnetic core comprising a plurality of laminae of magnetic material piled in a stack, each lamina consisting of a C-shaped piece and an H-shaped piece and a C-shaped piece in that sequence, one C-shaped piece having short arms and the other c-shaped piece having long arms and the H-shaped piece having short arms on one side of its crossbar and long arms on the other side, the ends of the short arms of the one C-shaped piece being abutted against the ends of the long arms of the-H-shaped piece and the ends of the long arms of the other. C-shaped piece being abutted against the-ends of the short arms of the H-sha'ped piece, the lengths of the short arms of the cned-shaped piece and of the H-shaped piece being all equal, the lengths of the long arms of the other C'shaped` piece' and of the H-shaped piece being all equal, the sum of the widths of the short arms of the one C-shaped piece being equal to the distance between the short arms of the H-shaped piece, and the sum of the width of the long arms of the other C-shaped piece being equal to the distance between the long arms of the H-shaped piece.

6. A laminated electromagnetic core compris# ing a plurality of laminae of magnetic material v piled in a stack, each lamina consisting of aC- shaped piece andan H-shaped piece and a C- shaped piece in that sequence, one C.shaped piece Ahaving short arms and the other C-shaped piece ERWIN E. FRANZ. 

